Quaternary ammonium salts of



Patented Aug. 7, 1951 QUATERNARY AMMONIUM SALTS OF PHOSPHORUS ACID ESTERS James H. Werntz, Wilmington, Del., assignor to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application May 25 1949, Serial No. 95,365

11 Claims.

This invention relates to chemical compounds, and more particularly to new quaternary ammonium salts and to methods for their preparation.

With the exception of the quaternary ammonium halides, the difficulty of preparing quaternary ammonium salts, depending for the most part on procedures involving the neutralization of expensive quaternary ammonium bases, has

in large measure retarded the investigation of salts containing other than halogen anions. For example, quaternary ammonium salts containing as the anionic portion the anion of an inorganic oxy acid of phosphorus or its esters are practically unknown.

This invention has as an object the prepare tion of new quaternary ammonium salts. A further object is a new type of salt of this kind consisting of a quaternary ammonium salt of an inorganic oxy acid of phosphorus. Further objects reside in methods for obtaining these salts.

I have now found that quaternary ammonium salts having attached to the nitrogen atom through oxygen an anion of an acid ester of an inorganic oxy acid of phosphorus can be prepared by reacting, preferably in the presence of an alcohol, at temperatures of 100 C. up to the decompo sition temperature of the resulting quaternary ammonium salt, a tertiary amine aliphatic in character, 1. e., aliphatic and cycloaliphatic tertiary amines, with an ester of an inorganic oxy acid. of phosphorus.

This invention also comprises the new mono quaternary ammonium salts which have attached to the nitrogen atom through oxygen the anion of a monobasic acid ester of an inorganic oxy acid of phosphorus wherein all but one of the acidic hydrogens are replaced by monovalent hydrocarbon radicals, and in which the remaining four valences of the nitrogen atom are attached to monovalent hydrocarbon radicals, at least three of these radicals being aliphatic in character, i. e., aliphatic and cycloaliphatic radicals.

The new mono quaternary ammonium salts can be represented by the formula (RMEN A wherein R is a monovalent aliphatic hydrocarbon radical, i. e., aliphatic and cycloaliphatic radicals, and R is a monovalent hydrocarbon radical and wherein A is the anion, attached to the nitrogen atom through oxygen, of a monobasic acid ester of an inorganic oXy acid of phosphorus wherein all but one of the acidic hydrogens are replaced by monovalent hydrocarbon radicals.

A more specific and preferred embodiment of the invention comprises the new quaternary ammonium phosphates having four of the valences of the nitrogen atom bonded to monovalent hydrocarbon radicals, i. e., aliphatic, cycloaliphatic and aromatic radicals, at least three of these being aliphatic in character, 1. e., aliphatic and cycloaliphatic radicals of up to 22 carbon atoms, the fifth valence of the nitrogen atom being attached through oxygen to the monovalent anion of phosphoric acid wherein the two remaining acidic hydrogens are replaced by monovalent hydrocarbon radicals, i. e., aliphatic, cycloaliphatic and aromatic radicals of up to 18 carbon atoms. These new quaternary ammonium phosphates can be represented by the formula,

wherein R is a monovalent aliphatic hydrocarbon radical, i. e., aliphatic and cycloaliphatic radicals containing from 1 to 22 carbon atoms, preferably alkyl and cycloalkyl radicals of up to 18 carbon atoms, and wherein R is a monovalent hydrocarbon radical, i. e., aliphatic, cycloaliphatic and aromatic radicals, preferably alkyl, cycloalkyl and aryl radicals of up to 18 carbon atoms.

The following equation represents what is believed to be the course of the reaction with typical reagents in the process of the invention:

(OHMN l2 25)3 a)aNOPO(OC12H2t)2 In actual practice the preparation of the quaternary ammonium salts of the invention can be carried out by charging into a suitable reactor the tertiary amine selected, for example triethylamine, the ester of an inorganic oxy acid of phosphorus, for example, triethyl phosphate and, if desired, an alcohol such an ethanol. The reactor is closed and then heated under autogenous pressure at a suitable temperature, preferably in the range of to C., for about 6 to 20 hours with agitation. After completion of the reaction, the reactor is cooled, opened and the contents discharged. The product is isolated by removal through distillation of the solvent, if .present, and any unreacted reagents.

The mole ratio of tertiary amine to ester may vary between 10:1 to 1:10. Best results are achieved, however, with a mole ratio of about 3:1. The use of alcoholic solvents ordinarily gives superior results, the preferable mole ratio of alcohol to tertiary amine being about 5:1, al-

though mole ratios of 1:1 to 15:1 can also be satisfactorily employed.

'Since the time necessary to complete the reaction decreases with increasing temperature, it is desirable, though not essential, to operate at a temperature as high as possible below the decomposition temperature of the quaternary ammonium salt formed. In general, the temperature range of 140-170 C. has been found the most satisfactory although the reaction may be carried out at a temperature as low as 100 C. Depending on the temperature and reagents employed as well as the presence of solvent, the time of reaction varies from 6 to 20 hours although at 140-170 0., 8-16 hours reaction time is usually satisfactory.

The invention is illustrated in further detail by the following examples in which parts, unless otherwise specified, are given by weight:

Example I A mixture of parts of triethylamine, 9 parts of triethyl phosphate and 14 parts of methanol was heated in a sealed glass tube for 8 hours at 150 C. After removal of the low boiling material under reduced pressure on the steam bath, 8.7 parts (61% yield) of light yellow water-soluble tetraethylammonium diethylphosphate was obtained. Analysis for nitrogen in this quaternary salt showed that it contained approximately 75% of the calculated value for this element.

Example II Using a molar ratio of 3:1 (tertiary amine to ester) an 81% conversion of triethyl phosphate to the desired quaternary ammonium salt was effected by heating a mixture of 30 parts of triethylamine, 18 parts of triethyl phosphate and 48 parts of methanol at 160 C. for hours in a sealed glass tube. The contents of the tube after removal of volatile materials at 140 C. under mm. pressure gave 23 parts of watersoluble crystalline tetraethylammonium/diethyl phosphate which on analysis showed a nitrogen content of 4.0%.

Example III The quaternary ammonium salt of the preceding example was also obtained (25% yield) without the use of alcoholic solvent. The reaction product obtained by heating 15 parts of triethylamine and 27 parts of triethyl phosphate in a sealed glass tube at 150* C. for 8 hours yielded 6.7 parts of tetraethylammonium diethyl phosphate by working up as described above. The nitrogen content of this product was shown to be comparable to that of the product of EX- ample I.

Example IV Employing the procedure described in Example II, 24 parts of triethylamine, 21 parts of tri-nbutyl phosphate and 45 parts of methanol yielded 17 parts (59% conversion of the tri-n-butyl phosphate) of oily n-butyl triethylammonium'dibutyl phosphate which was appreciably soluble in water.

Example V A mixture of 21 parts of triethylamine, 26 parts of tricresyl phosphate and 47 parts of methanol was heated for 10 hours at 160 C. in a. sealed glass tube. After evaporation of the reaction mixture under 15 mm. pressure at 150 C., 32 parts (97% conversion of the tricresyl phosphate) of oily tolyl triethylammonium dicresyl phosphate, which was appreciably soluble in water, was obtained.

4 Anal. Calcd. for C27H36N04P: N, 2.99%.

Found: N, 3.0%.

Example VI A mixture of 9 parts of dimethylcyclohexylamine, 13 parts of triethyl phosphate and 22 parts of methanol was heated in a sealed glass tube for 8 hours at 150 C. Fifteen and threetenths (15.3) parts of water-soluble oily ethyl dimethylcyclohexylammonium diethyl phosphate was obtained by evaporating the reaction mixture at C. under 3 mm. pressure. This corresponds to a 69% yield.

Example VII By employing the same procedure as described under Example VI, 42 parts (88% conversion of the triethyl phosphate) of crystalline watersoluble ethyl dimethyloctadecylammonium diethyl phosphate was obtained from the reaction of 29.7 parts of dimethyloctadecylamine, 18.2 parts of triethyl phosphate and 41.9 parts of methanol after heating for 10 hours at C.

When applied from water solutions this product imparted anti-static properties to nylon and cellulose acetate yarns, and also acted as a sof tener for viscose yarn. In tests as a lubricating oil detergent, the product which was soluble in mineral oil and dispersed carbon black in kerosene-mineral oil mixtures, had excellent suspending action for sludge.

Example VIII A mixture of 9 parts of triethanolamine, 11 parts of triethyl phosphate and 20 parts of methanol was heated in a sealed glass reactor for 8 hours at 150 C. On evaporation of the reaction mixture at 140 C. under 3 mm. pressure 14.9 parts of a water soluble oil was obtained.

The invention is not limited to the specific reactants illustrated in the foregoing examples, but embraces more broadly the reaction of a tertiary amine, aliphatic in character, with an ester of an inorganic oxy acid of phosphorus. The tertiary amines employed in the process of the invention are those having monovalent aliphatic hydrocarbon radicals, i. e., aliphatic and cyclo-,

aliphatic radicals, of up to 22 carbon atoms. Because of availability and suitable reactivity those in which the monovalent aliphatic hydrocarbon radicals are alkyl and cycloalkyl radicals of up to 18 carbon atoms are most preferred. Additional examples of these tertiary amines which may be substituted for those in the examples include trimethylamine, tri-n-propylamine, triisopropylamine, triisobutylamine, tri-n-amylamine, tri-n-octylamine, dimethylethylamine, dimethyl allylamine, diethylallylamine, dibutylallylamine, dimethyldodecylamine, diethylcyclohexylamine, tricyclohexylamine, dimethyloleylamine, tricrotylamine, dimethyldocosylamine, and the like.

As to the esters of inorganic oxy acids of phosphorus which can be employed in the process of this invention, the tri-esters of phosphoric, the tri-esters of phosphorous'and the tetraesters of pyrophosphoric acids, because of low cost and availability, are the most suitable, particularly those in which the ester groups attached to the phosphorus atom through oxygen are monovalent hydrocarbon radicals, i. e., aliphatic, cycloaliphatic and aromatic radicals, preferably alkyl, cycloalkyl and aryl radicals of up to 18 carbon atoms and more particularly those of 2 to '7 carbon atoms. Examples of these esters which can be sub itut d f r t e tri estcrs used in the examples are the trimethyl, tripropyl, tributyl, triisobutyl, triisoamyl tridodecyl, trihexadecyl, trioctadecyl, tricrotyl, triallyl, triphenyl, dodecyldicresyl, ethyl-o-phenylene, isobutyl-o-phenylone, and oleyldicresyl esters of phosphoric and phosphorous acids. Likewise the following tetraesters of pyrophoric acid such as tetramethylpyrophosphate and tetraethylpyrophosphate can be substituted for the triesters in the examples.

In the process of this invention, the use of alcoholic solvents particularly the monohydric alcohols, for example, alkanols and aralkanols of up to seven or eight carbon atoms usually give superior results. When processing aliphatic tertiary amines which contain at least one monovalent aliphatic hydrocarbon group of at least six carbon atoms, it is preferred to operate in the presence of these alcohols. Examples of monohydric alcohols which may be used include methanol, ethanol, propanol, isopropanol, isobutanol, n-butanol, cyclohexanol, benzyl alcohol, and the like.

The quaternary ammonium salts of this invention are appreciably water-soluble and useful as antistatic agents for nylon and cellulose acetate yarns and also as softeners for viscose yarns. Those quaternary ammonium salts which contain at least one monovalent aliphatic hydrocarbon radical, especially an alkyl or cycloalkyl radical, of six or more carbon atoms attached to the quaternary nitrogen atom, and in particular the quaternary ammonium ortho-phosphates of this structure, are especially desirable and preferred because they are soluble in hydrocarbon solvents and lubricating oils and possess excellent surface-tension lowering properties making them of especial value as lubricating oil detergents.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that this invention is not limited to the specific embodiments thereof except as defined in the appended claims.

I claim:

1. A process for obtaining quaternary ammonium salts of inorganic oxy acids of phosphorus, said process comprising heating at a temperature of from 100 C. to the decomposition temperature of the resulting quaternary ammonium salt, an amine from the group consisting of tertiary aliphatic and cycloaliphatic amines, with a completely esterified inorganic oxy acid of phosphorus in a mole ratio of from 1011 to 1:10, said oxy acid containing only phosphorus, hydrogen, and oxygen.

2. A process for obtaining quaternary ammonium salts of inorganic oxy acids of phosphorus, said process comprising heating in contact with a monohydric alcohol solvent at a temperature of from 100 C. to the decomposition temperature of the resulting quaternary ammonium salt, an amine from the group consisting of tertiary aliphatic and cycloaliphatic amines, with a completely esterified inorganic oxy acid of phosphorus in a mole ratio of from :1 to 1:10, said oxy acid containing only phosphorus, hydrogen and oxygen.

3. The process set forth in claim 1 in which said amine is one in which all the amino hydro gens are replaced by monovalent aliphatic hydrocarbon radicals containing from 1 to 22 carbon atoms, and in which said esterified inorganic oxy acid is a tri-ester of phosphoric acid wherein the radicals contained in the ester groups attached to the phosphorus atom through oxygen are monovalent hydrocarbon radicals containing from 1 to 18 carbon atoms.

4. The process set forth in claim 1 in which said amine is one in which all the amino hydrogens are replaced by monovalent aliphatic hydrocarbon radicals containing from 1 to 22 carbon atoms, and in which said esterified inorganic oxy acid is a tri-ester of phosphorous acid wherein the radicals containedin the ester groups attached to the phosphorus atom through oxygen are monovalent aliphatic hydrocarbon radicals containing from 1 to 18 carbon atoms.

5. The process set forth in claim 1 in which said amine is one in which all the amino hydrogens are replaced by monovalent aliphatic hy drocarbon radicals containing from 1 to 22 carbon atoms, and in which said esterified inorganic oxy acid is a tetraester of pyrophosphoric acid wherein the radicals contained in the ester groups attached to the phosphorus atom through oxygen are monovalent hydrocarbon radicals containing from 1 to 18 carbon atoms.

6. A mono quaternary ammonium salt which has attached to the nitrogen atom through oxygen the anion of an ester of an inorganic oxy acid of phosphorus, said acid containing only phosphorus, hydrogen, and oxygen and wherein all but one of the acidic hydrogens are replaced by monovalent hydrocarbon radicals, and in which the remaining four valences of the nitrogen atoms are attached to monovalent hydrocarbon radicals, at least three of these being from the group consisting of alkyl and cycloalkyl radicals.

7. A quaternary ammonium salt of the formula (R)3ENOPO(OR)3 wherein R is a monovalent aliphatic hydrocarbon radical containing from 1 to 22 carbon atoms, and R is a monovalent hydrocarbon radical containing from 1 to 18 carbon atoms.

8. As a new compound, tetraethylammonium diethyl phosphate.

9. As a new compound, tolyl triethylammonium dicresyl phosphate.

10. As a new compound, ethyl dimethylcyclohexylammonium diethyl phosphate.

11. As a new compound, ethyl dimethyloctadecylammonium diethyl phosphate.

JAMES H. WERNTZ.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,127,495 Tulleners Aug. 23, 1938 2,387,538 Smith Oct. 23, 1945 2,408,232 Smith Sept. 24, 1946 Certificate of Correction Patent No. 2,563,506 August 7, 1951 JAMES H. WERNTZ It is hereby certified that error appears in the printed specification of the above numbered patent requirlng correction as follows:

Column 2, line 40, for an, second occurrence, read 08; column 6, line 38, for atoms read atom;

and that the said Letters Patent should be read as corrected above, so that the same mayconform to the record of the case in the Patent Oflice.

Signed and sealed this 16th day of October, A. D. 1951.

THOMAS F. MURPHY,

Assistant Oommz'ssz'oner of Patents. 

1. A PROCESS FOR OBTAINING QUATERNARY AMMONIUM SALTS OF INORGANIC OXY ACIDS OF PHOSPHORUS, SAID PROCESS COMPRISING HEATING AT A TEMPERATURE OF FROM 100* C. TO THE DECOMPOSITION AT A TEMPERATURE TURE OF THE RESULTING WUATERNARY AMMONIUM SALT, AN AMINE FROM THE GROUP CONSISTING OF TERTIARY ALIPHATIC AND CYCLOALIPHATIC AMINES, WITH A COMPLETELY ESTERIFIED INORGANIC OXY ACID OF PHOSPHORUS IN A MOLE RATION OF FROM 10:1 TO 1:10, SAID OXY ACID CONTAINING ONLY PHOSPHORUS, HYDROGEN, AND OXYGEN. 